Magnetic material



June 2l, 1932. G. W ELMEN 1,864,054

MAGNETIC MATERIAL Filed July 29,1926

Perce/zMa/rgane S v x 1 1 l 2 4 o a /a /2 /4 /o 23* Cil Patented June 2l, 1932 stares PATENT oFFicE GUSTAJ? W. ELMEN, 0F LEONIA., NEW JERSEY, ASSIGNOR T0 WESTERN ELECTRIC COM- IPANY, INCORPORATED, 0F NEW YORK, N. Y., A CORPORATION 0E NEW- YORK MAGNETIC MATERIAL Application led July 29, 1926. Serial No. 125,697'.

rihis invention relates to magnetic materials and electromagnetic systems. It has wide application and is especially useful where the impressed magnetizing forces are small, as in signaling systems.

Among the important characteristics of the material of this invention are high permeability, especially at low magnetizing forces, small hysteresis and high resistivity.

As a material the inventionhas its embodiment in magnetic compositions containing manganese preferably with nickel and irona rlhe proportions of the ingredients and the treatment of the material may be varied to emphasize one or more of its characteristics.

This application is in part a. continuation of application, Serial No. 48,188, filed August 5, 1925. i 1

Magnetic materials have been variously employed in electrical systems for such purposes as the cores of loading coils, transform ers, magnetic modulators, etc., and for tractive electromagnets, for dynamos, motors, telephone receivers, telegraph relays, etc. Magnetic materials have also been employed for the continuous loading of signaling conductors, but, until recently, this use has been limited to relatively short cables for telephone purposes. Heretofore'the magnetic materials generally used for these purposes have been soft iron nd silicon steel. Recently, however, alloys coisisting chieiy of nickel and iron have been employed to great advantage, particularly in connection with signaling systems and apparatus, in which-the magnetic f forces-involved seldom exceed .2 auss. Such alloys and the method of producing them are disclosed in U. S. Patent 1,586,884, issued June 1, 1926 and in applicants copending application, referred to above.

The application referred to disc-loses a composition of nickel and iron with the addition of a third element, and having high permeability,. small hysteresis and eddy current losses, and high resistivity. Among the compositions mentioned is an alloy of nickel, iron and manganese. The present invention relates to magnetic materials consisting chiefly of nickel and manganese, or nickel, iron and manganese, and having higher permeability and manganese when the manganese content. and the iron content are varied and the nickel content is kept at approximately 78% of the nickel-iron-mang'anese content;

Fig. 3 Shows the change in resistivity of these alloys with varying percentages of manganese;

Fig. 4 indicates the change in hysteresis loss with variations in the percentage of manganese present; and

Fig. 5 is a perspective view of a signaling conductor loaded with the magnetic material of this invention in the form of tape.

It is readily seen from the curve of Fig. 1 that the initial ermeability of alloys containing about 8% nickel and varying amounts of iron and manganese decreases with increasing amounts of manganese. This curve was plotted from values obtained intesting a large number ofalloys of varying percentages of. iron and manganese, the nickel being kept at about 7 8%.. vOne of these alloys containing about 77% nickel, .75% manganese andthe balancev iron had an initial permeability of slightly over 7700, while for van alloy containing about 80% nickel and 20% man anese, the iron present being negligible, vthe initial permeability wasl slightly over 2000.

-As shown in Fig. 2, the maximum permeability of these alloys also decreases asthe percentage of manganese increases, but the rate of, decreasev in maximum permeability is greater for the lower percentagesfof manganese than the rate of decrease-in the-initial ioo permeability as shown in Fig. 1. -These values vary from 65,000 to about 5,600 in nearly a straight line proportion from the 75% alloy to the 20% alloy. Particular at- 5 tention is directed to the fact that an alloy composed Aoi substantially 80% nickel and 20% manganese with substantially no iron, has a higher initial permeability and a hi her maximum permeability than either nic (el or manganese taken alone. So far as is known, this is the first instance of an alloy of nickel and manganese having magnetic characteristics of this order.

The curve of Fig. 3 shows the variation in resistivity with varying percentages of manganese for alloys containing about 78% nickel and the balance manganese and iron. In the case of an alloy containing about 80% nickel and manganese, the resistivity is over 50 microhms per c. c., which property, together with its relatively high initial permeability, renders this material better than iron for use as a loading material for-signaling conductorsand for other uses where the mag- 2,5 netizing forces are small and the eddy eurrent loss may be large, as in transformer and inductance coil cores. y

A further advantage of the alloys of nickel and manganese and of nickel, iron and :man-

3 ganese is their very low hysteresis loss as compared with 'that of iron or silicon steel.

with change in composition and with a iux density B: 5000, is shown in Fig. 4. For the alloys having less t-han about 10% manganese thenhysteresisis approximately 80 ergs per cu. cm. per cycle. With higher percentages of manganese the hysteresis loss increases but is still considerably les than that of iron.

Although alloys containing about 78% nickel have been found to give the highest permeability and to be preferable for many purposes, these characteristics are not limited to alloys containing 78% nickel since, by decreasing the percentage of nickel in the material, alloys having a higher resistivity may be obtained although the initial permeability of such alloys is ordinarily decreased. Thus, for example, it has been found that an alloy comprising approximately 70% nickel` 20% iron and 10% manganese has an initial permeability of 3580 and a resistivity of 55.7 microhmcms. For certain purposes, as in the caselof loading material for signaling conductors, an alloy of this character may be preferable to one having a higher initial permeability but a lower resistivity.

o to this invention, nickel, iron and manganese p Thevariations of hysteresis loss in these alloysln preparing magnetic materials according vduotors a particularly suitable form of the alloy is that of tape about .006 inch thick and about .125 inch in width.

In order to give the alloy'the desired characteristics, it is necessary to subject it to a process of heat treatment which will be dependent upon the composition of the 4alloy and upon the particular characteristics which it is desired to produce in the material. An example of this heat treatment is to heat the alloy to about 1100o C. and maintain it at that temperature for a period of approximately one hour and subsequently cool the material slowly. The rate of cooling and the temperature to which the material is heated may be determined by experiment in each case in order that those characteristics sought in the material may be produced to the desired degree. An average rate of cooling which has been found to bc suitable is approximately five degrees per minute. The temperature to which the material is heated may be considerably lower than 11000 C. or in some cases it may be higher.

A .modification of this heat treatment, which is preferable in some instances, is 'to reheat the alloy, after the initial heat treatment outlined above, to a temperature somewhat above its magnetic transition point. The material is then cooled to room temperature, past themagnetic transition point at a certain rate which should be determined with each alloy but which is preferably faster than that employed in an anneal but not so fast as to set up strains in the material due to uneven cooling throughout the body. If desired, the reheating of the alloy may be omitted and the cooling from 1100 C. may be vcarried out in two steps at two dierent rates of cooling, that is, cooling from 1100D C. to a temperature slightly above the mag-l netic transition point at yone rate and from that point to room temperature at another rate. l

Whenthe material is to be used for the continuous loading of signaling conductors, it is first formed into tape having the dimensions stated'above. This tape is produced by working the alloy into the form of a rod or bar by repeated steps ot swaging and annealing. The bar 1s subsequently drawn down to the form of wire of about No. 20 B. & S. gauge, and passed between rollers whereby it is flattened into tape of the proper thickness. This tape is next passed through cutting rolls or discs which trim its edges squarely on both sides and give the tape a uniform width.

The stranded conductor shown` in Fig. 5 comprises a central cylindrical wire 11, enveloped by a plurality of surrounds 12 which are shaped to'it together closely to form a cylindrical annulus about the central wire. The magnetic material 13, ini the form of tape, is wrapped helically about the stranded copper core as Y- disclosed in U. S. Patent 1,586,887, issued June 1, 1926.` When it is desired to use the :loading material in the form of wire rather than tape, the drawing process as outlined above is continueduntil the wire has the desired dimensions.

The taped conductor isthen given its final 'heat treatmentv by drawing it lengthwise through an electric furnace of the muiile type having a horizontal iron heating tube extending through the furnace and projecting a considerable distance beyond. The furnace is maintained at the optimum temperature 'for the composition of the alloy being employed. The length of the pass through the heating tube and the rate at which the conductor is moved are chosen so as to produce the most desirable magnetic characteristics in the loaded conductor.' After cooling, the conductor is insulated andA formed into a cable in the usualmanner.

It will be found that certain of these alloys are better suited for some particular usesthan others, and that the characteristics of any alloy may be varied by giving the material different heat treatments. No attempt has therefore been made to give an exhaustive analysis of the characteristics of each composition but merely to point out generally the characteristicadvantages and uses of certain alloys and suggest typical methods of producing the same, with the understandin Aand intention that other similar compositlons and methods of production are comprised within the spirit and scope of the invention as described and claimed.

What is claimed is: 1. A magnetic material comprising substantial quantities of nickel and manganese 40 as essential elements thereof and having highl er permeability than iron at low magnetizing 4s A magnetic material comprising nickel,

iron and manganese as essential elements thereof, in which the iron and manganese contents each are not more than 20% of the nickel-iron-manganese content... I

5. A magnetic material consistin of not less than? 0% nickel and the remain er manganese and iron. l l 6. A'magnetic material consisting of not less than 70% nickel, a substantial amount ofbut not more than 20% manganese and the "5 remainder iron.

less than nickel, a substantial amount of but not morethan 20% manganese and the remainder iron and in combination therewith an electrical conductor in inductive relation with said material.

10. A transmission line continuously loaded with a magnetic material consisting of nickel, iron and manganese.

11. A loaded conductor comprising a conducting core and a'layer of loading material wrapped helically thereabout, said loading material Vbeing chiefly composed of nickel, iron and manganese, the nickel comprising not less than 70% of the whole, the manganese comprising not more than 20% of the whole and the remainder iron.

12. A magnetic material of high permeability at low magnetizing forces such as occur in the magnetic material of continuously loaded signaling conductors, of low coercive force, and high specific resistance, consisting of an alloy of nickel greater than about 40%, manganese from a small amount up to `about 20%, and the balance chiey iron.

-13. A magnetic material comprising 60% to 85% nickel, 15% to 40% iron and 4% to 20% manganese.

14. A magnetic alloy of iron, nickel and manganese having an initial permeability greater than `2000 and a resistivity greater than 20 microhm-cms.

15;'Magnetizable material consisting of a basic alloy of iron and nickel, wherein the nickel content amounts to at least 40% and to which alloy, manganese from 2% to 20% is added.

y In witness'whereof, `I hereunto subscribe my name this 22nd day of July A. D., 1926.

GUSTAF W. ELMEN. 

